Wireless device and power control method

ABSTRACT

The present disclosure provides a power control method and a wireless device, in a cluster comprised of wireless devices including a first wireless device and a second wireless device, comprising: receiving power control information including a second data channel transmission power, from the second wireless device; determining a first data channel transmission power based on the second data channel transmission power; and controlling data channel transmission power of the first wireless device according to the first data channel transmission power; wherein, the first data channel transmission power is a power allowing the first wireless device to reach all wireless devices in the cluster, and the second data channel transmission power is a power allowing the second wireless device to reach all wireless devices in the cluster.

BACKGROUND Technical Field

The present disclosure relates to the communication field, and inparticular, to a wireless device and a power control method in awireless communication system.

Description of the Related Art

D2D (device to device) is a new topic in 3GPP LTE release 12, and themain target for such study item is to realize direct device-to-devicecommunication. D2D communication could happen within network coverage(for commercial case) and without network coverage (for public safety).

FIG. 1 is a schematic diagram showing two D2D communication scenarios.As shown in FIG. 1, in a scenario 100A shown in the left part of FIG. 1,two wireless devices 101 and 102 realize direct device-to-devicecommunication, within network coverage by eNode B 103; while in theother scenario 100B shown in the right part of FIG. 1, two wirelessdevices 104 and 105 realize direct device-to-device communicationwithout network coverage.

In Rel.12, the focus on D2D communication is mainly out-of-networkcoverage scenario and broadcasting traffic.

One issue on out-of-network coverage scenario is the structure of D2Dcommunication. Currently there are two candidates for the structure ofD2D communication basically: 1) centralized structure as shown in FIG.2A; and 2) distributed structure as shown in FIG. 2B.

FIGS. 2A and 2B are schematic diagrams showing a centralized structureand a distributed structure in D2D communication, respectively.

In FIG. 2A, the solid line represents the data signal and the dashedline represents the control signal. It can be seen that there are twokinds of wireless device (which may be also referred to as userequipment, UE), the cluster head (or master UE) 201 and the slave UEs202A-202D, in the centralized scenario. Signaling is controlled by thecluster head, but data could be directly transmitted from a slave UE toanother slave UE in such scenario.

In FIG. 2B, similarly, the solid line represents the data signal and thedashed line represents the control signal. It can be seen that, there isno definition of cluster head (or master UE) and slave UE in thedistributed scenario. The identifications of all the UEs 203A-203E areequal. The control signaling and data are both transmitted from atransmitting UE to a receiving UE.

Another issue on D2D communication is the power control problem.Currently, there is no power control based on most companies'understanding. Thus a maximum power transmission is the basicassumption. This would cause large power consumption and interference toother UEs.

FIG. 3 is a schematic diagram showing the problem caused due to themaximum power transmission. As shown in FIG. 3, it is desirable for atransmitting UE 301 to transmit data and signaling to the receiving UEs302A-302C in a cluster to which the transmitting UE 301 belongs. Thus,the optimal transmission power range is as shown by the ellipse in thedashed line in FIG. 3. However, the maximum transmission power range isas shown by the ellipse in the solid line in FIG. 3. Therefore, itcauses not only a large power consumption of the transmitting UE 301,but also a large interference to the non-targeted UEs 303A and 303B.

BRIEF SUMMARY

The present disclosure is made in consideration of the above aspects.

According to a first aspect of the present disclosure, a power controlmethod performed by a first wireless device is provided, in a clustercomprised of wireless devices including the first wireless device and asecond wireless device, comprising: receiving power control informationincluding a second data channel transmission power, from the secondwireless device; determining a first data channel transmission powerbased on the second data channel transmission power; and controllingdata channel transmission power of the first wireless device accordingto the first data channel transmission power; wherein, the first datachannel transmission power is a power allowing the first wireless deviceto reach all wireless devices in the cluster, and the second datachannel transmission power is a power allowing the second wirelessdevice to reach all wireless devices in the cluster.

According to a second aspect of the present disclosure, a power controlmethod performed by a second wireless device is provided, in a clustercomprised of wireless devices including a first wireless device and thesecond wireless device, comprising: acquiring second data channeltransmission power; and transmitting power control information includingthe second data channel transmission power, to the first wirelessdevice; wherein, data channel transmission power of the first wirelessdevice is controlled, according to a first data channel transmissionpower determined based on the second data channel transmission power;the first data channel transmission power is a power allowing the firstwireless device to reach all wireless devices in the cluster, and thesecond data channel transmission power is a power allowing the secondwireless device to reach all wireless devices in the cluster.

According to a third aspect of the present disclosure, a power controlmethod in a cluster comprised of wireless devices including a firstwireless device and a second wireless device is provided, comprising:acquiring a second data channel transmission power by the secondwireless device; transmitting power control information including thesecond data channel transmission power to the first wireless device, bythe second wireless device; receiving the power control information fromthe second wireless device, by the first wireless device; determining afirst data channel transmission power based on the second data channeltransmission power, by the first wireless device; and controlling datachannel transmission power of the first wireless device according to thefirst data channel transmission power, by the first wireless device;wherein, the first data channel transmission power is a power allowingthe first wireless device to reach all wireless devices in the cluster,and the second data channel transmission power is a power allowing thesecond wireless device to reach all wireless devices in the cluster.

According to a fourth aspect of the present disclosure, a wirelessdevice is provided, in a cluster comprised of wireless devices includingthe wireless device as a first wireless device, and a second wirelessdevice, comprising: a receiver which receives power control informationincluding a second data channel transmission power from the secondwireless device; a determining unit which determines a first datachannel transmission power based on the second data channel transmissionpower; and a controller which controls data channel transmission powerof the first wireless device according to the first data channeltransmission power; wherein, the first data channel transmission poweris a power allowing the first wireless device to reach all wirelessdevices in the cluster, and the second data channel transmission poweris a power allowing the second wireless device to reach all wirelessdevices in the cluster.

According to a fifth aspect of the present disclosure, a wirelessdevice, in a cluster comprised of wireless devices including a firstwireless device and the wireless device as a second wireless device,comprising: an acquiring unit which acquires second data channeltransmission power; and a transmitter which transmits power controlinformation including the second data channel transmission power, to thefirst wireless device; wherein, data channel transmission power of thefirst wireless device is controlled, according to a first data channeltransmission power determined based on the second data channeltransmission power; the first data channel transmission power is a powerallowing the first wireless device to reach all wireless devices in thecluster, and the second data channel transmission power is a powerallowing the second wireless device to reach all wireless devices in thecluster.

According to the power control method and the wireless device of someaspects of the present disclosure, the power consumption of the wirelessdevice and the interference to non-targeted wireless devices can bereduced in different scenarios of the D2D communication.

The foregoing is a summary and thus contains, by necessity,simplifications, generalization, and omissions of details. Otheraspects, features, and advantages of the devices and/or processes and/orother subject matters described herein will become apparent in theteachings set forth herein. The summary is provided to introduce aselection of concepts in a simplified form that are further describedbelow in the Detailed Description. This summary is not intended toidentify key features or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in determining the scopeof the claimed subject matter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and/or other aspects and advantages of the present disclosure willbecome more distinct and easier to be understood in a detaileddescription of embodiments of the present disclosure below incombination with attached drawings, in which:

FIG. 1 is a schematic diagram showing two scenarios of D2Dcommunication;

FIGS. 2A and 2B are schematic diagrams showing a centralized structureand a distributed structure in D2D communication, respectively;

FIG. 3 is a schematic diagram showing the problem caused due to maximumpower transmission in D2D communication;

FIG. 4 is a flowchart showing a power control method by a wirelessdevice according to an embodiment of the present disclosure;

FIG. 5 is a flowchart showing a power control method by a wirelessdevice according to another embodiment of the present disclosure;

FIG. 6 is a block diagram showing a schematic structure of a wirelessdevice according to an embodiment of the present disclosure;

FIG. 7 is a block diagram showing a schematic structure of a wirelessdevice according to another embodiment of the present disclosure;

FIG. 8 is a schematic diagram showing a D2D communication scenarioaccording to a first embodiment of the embodiment;

FIG. 9 is a schematic diagram showing the basic principle applied to theD2D communication scenario of the first embodiment;

FIG. 10 is a schematic diagram showing a D2D communication scenarioaccording to a second embodiment of the embodiment; and

FIG. 11 is a schematic diagram showing a D2D communication scenarioaccording to a third embodiment of the embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part thereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. It will be readily understood that the aspects ofthe present disclosure can be arranged, substituted, combined, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated and make part of this disclosure.

FIG. 4 is a flowchart showing a power control method by a wirelessdevice (user equipment, UE) according to the embodiment of the presentdisclosure. The UE and at least one other UE may form a cluster, and theUE may perform direct communication with the other UE, with atransmission power large enough to reach all the UEs in the cluster. Inthe following description, in order to distinguish, the wireless devicewill be referred to as the first wireless device, and the other wirelessdevice will be referred to as the second wireless device.

As shown in FIG. 4, in the embodiment of the present disclosure, at thefirst wireless device side, first, at Step 401, power controlinformation including a second data channel transmission power isreceived from the second wireless device. The second data channeltransmission power is a power allowing the second wireless device toreach all wireless devices in the cluster. That is, the second datachannel transmission power may not be the maximum transmission power ofthe second wireless device, as long as it is large enough to allow thesecond wireless device to communicate with all wireless devicesincluding the first wireless device in the cluster.

Then, at Step 402, a first data channel transmission power is determinedbased on the second data channel transmission power. Similarly to thesecond data channel transmission power, the first data channeltransmission power is a power allowing the first wireless device toreach all wireless devices in the cluster. That is, the first datachannel transmission power may not be the maximum transmission power ofthe first wireless device, as long as it is large enough to allow thefirst wireless device to communicate with all wireless devices includingthe second wireless device in the cluster. The determination process ofthe first data channel transmission power will be described later indetail in combination with several embodiments.

Then, after determining the first data channel transmission power, atStep 403, the data channel transmission power of the first wirelessdevice is controlled according to the first data channel transmissionpower. For example, the data channel transmission power of the firstwireless device may be controlled to be the first data channeltransmission power.

FIG. 5 is a flowchart showing a power control method performed by thesecond wireless device. As shown in FIG. 5, in the embodiment, at thesecond wireless device side, first, the second data channel transmissionpower is acquired at Step 501. The process of acquiring the second datachannel transmission power will be described later in detail incombination with several embodiments.

Then, the power control information including the second data channeltransmission power is transmitted to the first wireless device at Step502. As described above, the power control information is used todetermine the first data channel transmission power, so that the datachannel transmission power of the first wireless device is controlledaccording to the first data channel transmission power. The meanings ofthe first data channel transmission power and the second data channeltransmission power have been described above, and are not described herein detail.

That is, in the embodiments of the present disclosure, for the clusterincluding the first wireless device and the second wireless device, apower control method is provided as follows. First, the second datachannel transmission power is acquired by the second wireless device.Then, the power control information including the second data channeltransmission power is transmitted to the first wireless device, by thesecond wireless device. Accordingly, the power control information isreceived from the second wireless device, by the first wireless device.Next, the first data channel transmission power is determined based onthe second data channel transmission power, by the first wirelessdevice. At last, the data channel transmission power of the firstwireless device is controlled according to the first data channeltransmission power, by the first wireless device.

FIG. 6 is a block diagram showing the schematic structure of a wirelessdevice 600 according to the embodiment of the present disclosure. Asshown in FIG. 6, the wireless device 600 as the first wireless devicecomprises a receiver 601 which receives power control informationincluding a second data channel transmission power from the secondwireless device; a determining unit 602 which determines a first datachannel transmission power based on the second data channel transmissionpower; and a controller 603 which controls data channel transmissionpower of the first wireless device according to the first data channeltransmission power.

Similarly to those described with reference to FIGS. 4 and 5, the firstdata channel transmission power is a power allowing the first wirelessdevice to reach all wireless devices in the cluster, and the second datachannel transmission power is a power allowing the second wirelessdevice to reach all wireless devices in the cluster.

The wireless device 600 according to the embodiment may optionallyinclude a CPU (Central Processing Unit) 610 for executing relatedprograms to process various data and control operations of respectiveunits in the wireless device 600, a ROM (Read Only Memory) 613 forstoring various programs required for performing various process andcontrol by the CPU 610, a RAM (Random Access Memory) 615 for storingintermediate data temporarily produced in the procedure of process andcontrol by the CPU 610, and/or a storage unit 617 for storing variousprograms, data and so on. The above receiver 601, the determining unit602, the controller 603, CPU 610, ROM 613, RAM 615 and/or storage unit617 etc. may be interconnected via data and/or command bus 620 andtransfer signals between one another.

Respective units as described above do not limit the scope of thepresent disclosure. According to one implementation of the disclosure,the functions of the above receiver 601, the determining unit 602 andthe controller 603 may be implemented by hardware, and the above CPU610, ROM 613, RAM 615 and/or storage unit 617 may not be necessary.Alternatively, the functions of the above receiver 601, the determiningunit 602 and the controller 603 may also be implemented by functionalsoftware in combination with the above CPU 610, ROM 613, RAM 615 and/orstorage unit 617 etc.

FIG. 7 is a diagram showing a schematic structure of a wireless device700 according to the embodiment of the present disclosure. As shown inFIG. 7, the wireless device 700 as the second wireless device comprisesan acquiring unit 701 which acquires second data channel transmissionpower; and a transmitter 702 which transmits power control informationincluding the second data channel transmission power, to the firstwireless device. The data channel transmission power of the firstwireless device is controlled, according to a first data channeltransmission power determined based on the second data channeltransmission power.

Similarly to those described with reference to FIGS. 4 and 5, the firstdata channel transmission power is a power allowing the first wirelessdevice to reach all wireless devices in the cluster, and the second datachannel transmission power is a power allowing the second wirelessdevice to reach all wireless devices in the cluster.

The wireless device 700 according to the embodiment may optionallyinclude a CPU (Central Processing Unit) 710 for executing relatedprograms to process various data and control operations of respectiveunits in the wireless device 700, a ROM (Read Only Memory) 713 forstoring various programs required for performing various process andcontrol by the CPU 710, a RAM (Random Access Memory) 715 for storingintermediate data temporarily produced in the procedure of process andcontrol by the CPU 710, and/or a storage unit 717 for storing variousprograms, data and so on. The above acquiring unit 701, transmitter 702,CPU 710, ROM 713, RAM 715 and/or storage unit 717 etc. may beinterconnected via data and/or command bus 720 and transfer signalsbetween one another.

Respective units as described above do not limit the scope of thepresent disclosure. According to one implementation of the disclosure,the functions of the above acquiring unit 701 and transmitter 702 may beimplemented by hardware, and the above CPU 710, ROM 713, RAM 715 and/orstorage unit 717 may not be necessary. Alternatively, the functions ofthe above acquiring unit 701 and transmitter 702 may also be implementedby functional software in combination with the above CPU 710, ROM 713,RAM 715 and/or storage unit 717 etc.

In the power control methods shown in FIGS. 4 and 5 and the wirelessdevices shown in FIGS. 6 and 7, the data channel transmission power ofthe first wireless device may be determined based on the data channeltransmission power of the second wireless device as described above. Inthe following, a detailed description will be made to the power controlmethod in combination with several embodiments.

First Embodiment

In the first embodiment, the data channel transmission power of thefirst wireless device is determined not only based on the transmissionpower of the second wireless device, but also based on a transmissionpath loss between the first wireless device and the second wirelessdevice.

FIG. 8 is a schematic diagram showing a D2D communication scenarioaccording to the first embodiment of the embodiment. As shown in FIG. 8,the UEs 801-803 form a UE cluster 800 with a centralized structure,wherein the UE 801 functions as the cluster head (CH), while the UEs 802and 803 function as the slave UEs. Assume that the UE2 803 is thetransmitting UE and the UE1 802 is the receiving UE. The UE2 803corresponds to the first wireless device described above with referenceto FIGS. 4-7, and the CH 801 corresponds to the second wireless devicedescribed above with reference to FIGS. 4-7.

FIG. 9 is a schematic diagram showing the basic principle applied to theD2D communication scenario of the first embodiment shown in FIG. 8. Asshown in FIG. 9, the power used for compensating path loss between UE2and CH is represented by the arrow marked with symbol A. The datachannel transmission power of the CH is represented by the arrow markedwith symbol B. The power necessary for the transmitting UE2 to transmitdata signal to the receiving UE1 is represented by the arrow marked withsymbol C. Then, the sum of A and B is always larger than or equal to Cregardless of CH's position. In other words, whatever CH's position is,the sum of A and B could always satisfy UE2's transmission requirement.In most cases, the power value based on the sum of A and B exceeds thereal requirement.

Based on this principle, the data channel transmission power of thetransmitting UE2 may be determined based on the data channeltransmission power of the CH, and the transmission path loss between theUE2 and the CH.

In particular, the data channel transmission power of the transmittingUE2 may be derived from the following equation (1):P_slave=P_pathloss+P_CH  (1)Wherein, P_slave is the data channel transmission power of the slave UE,i.e., the first wireless device described above with reference to FIGS.4-7. P_CH is the data channel transmission power of the CH, i.e., thesecond wireless device described above with reference to FIGS. 4-7.P_pathloss is the transmission path loss between the first wirelessdevice and the second wireless device.

Further, in order to compensate for the channel fading, a margin powervalue may be introduced. That is, the data channel transmission power ofthe transmitting UE2 may be derived from the following equation (2):P_slave=P_pathloss+P_CH+P_margin  (2)Wherein, the meanings of P_(slave), P_CH, and P_pathloss are the same asthose in the equation (1), and P_margin is the margin power value forcompensating for the channel fading, such as the fast fading. Thedetermination of the margin power value is known to those skilled in theart, and will not be described here in detail.

In the above equations (1) and (2), the transmission path loss may bedetermined from the reference signal transmission power and receptionpower as follows:P_pathloss=P_CH _(RS) −RSRP  (3)Wherein, P_CH_(RS) is the reference signal transmission power of the CH,and RSRP is the reference signal reception power measured at the slaveUE2.

The above equation (3) may be substituted into the above equation (1) or(2). In particular, the reference signal transmission power P_CH_(RS) ofthe CH may be the same as the data channel signal transmission powerP_CH of the CH or may be different. When they are the same, for example,the above equation (2) may be further expressed as follows:

$\begin{matrix}\begin{matrix}{{P_{—}{slave}} = {{P_{—}{pathloss}} + {P_{—}{CH}} + {P_{—}{margin}}}} \\{= {{P_{—}{CH}} - {RSRP} + {P_{—}{CH}} + {P_{—}{margin}}}} \\{= {{2 \times P_{—}{CH}} - {RSRP} + {P_{—}{margin}}}}\end{matrix} & (4)\end{matrix}$

In the first embodiment of the present disclosure, on one hand, thesecond data channel transmission power may be included in the powercontrol information and signaled by the second wireless device to thefirst wireless device. On the other hand, the transmission path lossbetween the first wireless device and the second wireless device may bedetermined based on a reference signal reception power measured at thefirst wireless device, and a reference signal transmission power of thesecond wireless device which, generally, may be the same as the seconddata channel transmission power signaled to the first wireless device.Thereby, the first wireless device may determine its data channeltransmission power based on the above equations.

With the first embodiment of the present disclosure, the large powerconsumption of the first wireless device and the interference tonon-targeted wireless devices can be avoided, due to the accurate powercontrol irrespective to the position of the second wireless device (theCH).

Second Embodiment

In the second embodiment of the present disclosure, the first datachannel transmission power is determined only based on the second datachannel transmission power, when the second wireless device isdetermined to be at an edge of the cluster.

FIG. 10 is a schematic diagram showing a D2D communication scenarioaccording to the second embodiment of the embodiment. As shown in FIG.10, the UEs 1001-1003 form a UE cluster 1000 with a centralizedstructure, wherein the UE 1001 functions as the cluster head (CH), whilethe UEs 1002 and 1003 function as the slave UEs. Assume that the UE11002 is the transmitting UE and the UE2 1003 is the receiving UE. TheUE1 1002 corresponds to the first wireless device described above withreference to FIGS. 4-7, and the CH 1001 corresponds to the secondwireless device described above with reference to FIGS. 4-7.

In FIG. 10, the position of the CH 1001 is known and it is located atthe edge of cluster. Since the CH's data channel transmission powercould compensate path loss of farthest UE and any slave UE's datachannel transmission power used to compensate path loss to other UEsshould not exceed CH's data channel transmission power, the UE1 1002 canreach the farthest UE2 1003 by using the same power as the CH's datachannel transmission power. That is, in this embodiment, the first datachannel transmission power may be the same as the second data channeltransmission power.

Further, similarly to that in the first embodiment, considering thechannel fading, the margin power value may also be included, and thefirst data channel transmission power may be derived as follows:P_slave=P_CH+P_margin  (5)

The meanings of the parameters in the equation (5) are the same as thosedescribed in the first embodiment, and will not be described here indetail.

Therefore, in this embodiment, the key matter is to know the position ofCH. In practical implementations, there are many ways to locate the CH.For example, the position of CH may be determined from a positioningsystem, a positioning channel or a positioning signal. For anotherexample, the position of CH may be determined from a pre-codingcharacter. For a further example, the position of CH may be determinedfrom a beamformed reception signal at the CH. The detailed process oflocating the CH is known to those skilled in the art, and will not bedescribed here in detail.

With the second embodiment of the present disclosure, similarly, thelarge power consumption of the first wireless device and theinterference to non-targeted wireless devices can be avoided.Furthermore, by comparing the equation (5) of the second embodiment withthe equation (2) of the first embodiment, it can be seen that the termof P_pathloss is removed. Therefore, the data channel transmission powerof the first wireless device may be further reduced by utilizing theposition information of the second wireless device.

Third Embodiment

In either the first embodiment or the second embodiment, the datachannel transmission power of the first wireless device is relativelyfixed after being determined. However, with the change of the secondwireless device's position, the data channel transmission power of thefirst wireless device may also be changed accordingly.

In particular, in the third embodiment, the first data channeltransmission power may be changed between a power based on the seconddata channel transmission power and a transmission path loss between thefirst wireless device and the second wireless device, and a power onlybased on the second data channel transmission power, according to theposition of the second wireless device.

FIG. 11 is a schematic diagram showing a D2D communication scenarioaccording to the third embodiment of the embodiment. As shown in FIG.11, the UEs 1101-1103 form a UE cluster 1100 with a centralizedstructure, wherein the UE 1101 functions as the cluster head (CH), whilethe UEs 1102 and 1103 function as the slave UEs. Assume that the UE11102 is the transmitting UE and the UE2 1103 is the receiving UE. TheUE1 1102 corresponds to the first wireless device described above withreference to FIGS. 4-7, and the CH 1101 corresponds to the secondwireless device described above with reference to FIGS. 4-7.

In case the CH 1101 is in position 1, i.e., at the edge of the cluster,the power control method based on the second embodiment may be used.That is, the data channel transmission power of the UE1 1102 isdetermined only based on the data channel transmission power of the CH1101. In case the CH 1101 is moved into position 2, i.e., not at theedge of the cluster, the power control method based on the firstembodiment may be used. That is, the data channel transmission power ofthe UE1 1102 is determined based on the data channel transmission powerof the CH 1101 and the transmission path loss between the CH 1101 andthe UE1 1102.

The information on which power control method is used may be signaled bya higher layer signaling or a L1 signaling.

With the third embodiment of the present disclosure, similarly, thelarge power consumption of the first wireless device and theinterference to non-targeted wireless devices can be avoided. Further,an optimized power control scheme can be used corresponding to differentscenarios, e.g., different positions of the second wireless device.

Fourth Embodiment

In the first to three embodiments, description has been made on how tocontrol the data channel transmission power of the first wirelessdevice, e.g., the slave UE. In the following fourth embodiment, thepower control method with respect to the second wireless device, e.g.,the CH, will be described.

Assuming the same scenario as that in FIG. 8, the data channeltransmission power of the second wireless device may be determined froma reference signal.

In particular, the data channel transmission power of the secondwireless device may be determined at the first wireless device side orthe second wireless device side. For an example, the data channeltransmission power of the second wireless device may be determined atthe first wireless device side, from a reference signal reception powermeasured at the first wireless device, a reference signal transmissionpower of the second wireless device and a minimum signal reception powercommon to all the wireless devices in the cluster.

That is, as shown in FIG. 8, the data channel transmission power of theCH 801 may be determined from the following equation (6):P_CH=P_CH _(RS) −RSRP+P_threshold  (6)Wherein, P_threshold is the minimum signal reception power common to allthe wireless devices in the cluster, and the meanings of P_CH, P_CH_(RS)and RSRP are the same as those in the above equations, and will not bedescribed here in detail.

It is to be noted that the above description has been made withreference to two slave UEs. However, it also applies to more than twosalve UEs. In particular, suppose that the cluster comprise multiplewireless devices including the first wireless device, the secondwireless device, and a third wireless device, and the second datachannel transmission power may be determined from a minimum valuebetween the reference signal reception power measured at the firstwireless device and a reference signal reception power measured at thethird wireless device, the reference signal transmission power of thesecond wireless device, and a minimum signal reception power common toall the wireless devices in the cluster, which may be expressed by thefollowing equation (7):P_CH=P_CH _(RS)−min(RSRP_ue ₁ ,RSRP_ue ₂ ,RSRP_ue ₃ , . . . RSRP_ue_(n))+P_threshold  (7)Wherein, min(RSRP_ue₁,RSRP_ue₂,RSRP_ue₃, . . . RSRP ue_(n)) is theminimum value of the reference signal reception power measured at all (anumber of n) slave UEs in the cluster, and the meanings of P_CH,P_CH_(RS), and P_threshold are the same as those described in the aboveequations, and will not be described here in detail.

Further, it is to be noted that the above description has been made withreference to the case in which the second data channel transmissionpower is determined at the first wireless device side. However, asdescribed above, it may also be determined at the second wireless deviceside. That is, the second data channel transmission power may bedetermined from a reference signal reception power measured at thesecond wireless device, a reference signal transmission power of thefirst wireless device and a minimum signal reception power common to allthe wireless devices in the cluster.

When the cluster comprises multiple wireless devices including the firstwireless device, the second wireless device and the third wirelessdevice, similarly to the above example, the second data channeltransmission power may be determined from a minimum value between thereference signal reception power measured at the second wireless deviceand a reference signal reception power measured at the third wirelessdevice, the reference signal transmission power of the first wirelessdevice, and a minimum signal reception power common to all the wirelessdevices in the cluster.

The detailed processing of determining the second data channeltransmission power is similar to those in the above example, and willnot be described here in detail.

Further, it is to be noted that the above description has been made withreference to the centralized D2D communication scenario. However, italso applies to the distributed D2D communication scenario. In thiscase, P_CH in the above equation (7) means the data channel transmissionpower of a target UE, e.g., a transmitting UE, P_CH_(RS) means thereference signal transmission power of the target UE, andmin(RSRP_ue₁,RSRP_ue₂,RSRP_ue₃, . . . RSRP_ue_(n)) means the minimumvalue of the reference signal reception power measured at all the other(a number of n) UEs, e.g., all the receiving UEs, in the cluster.

With the fourth embodiment of the present disclosure, the transmissionpower of a transmitting wireless device can be optimized based on thecoverage of receiving UEs, so that the transmitting wireless device doesnot always adopt the maximum transmission power, and the powerconsumption of the transmitting wireless device can be reduced.

Fifth Embodiment

In the above four embodiments, power control method on the data channelhave been described. However, the power control method of the presentdisclosure may also be applied to the control channel, as in thefollowing fifth embodiment.

In particular, in one example, the control channel transmission power ofa wireless device may be determined from the data channel transmissionpower and an offset value as in the following equation (8).P_control=P_data+P_offset  (8)Wherein, P_control is the control channel transmission power of awireless device, P_data is the data channel transmission power of thesame wireless device which may be determined according to any one of theabove embodiments, and P_offset is the offset or compensation factorused for the control channel, which may be specified or configured by ahigh layer signaling, such as a RRC signaling.

Therefore, with this example, the power of other channel, such as thecontrol channel, does not need to be a fixed or maximum value, and maybe optimized depending on the situation, just like the power of datachannel as described in the above embodiments.

In another example, in order to guarantee the robustness of the controlchannel, the power control of the control channel may be independentwith that of the data channel. For example, the control channel couldalways be set with the maximum power value regardless of the datachannel's situation.

Variants

In the above first to fifth embodiments, the power control informationtransmitted from the second wireless device to the first wireless deviceincludes the data channel transmission power of the second wirelessdevice, i.e., the second data channel transmission power, and then thefirst wireless device determines its own data channel transmissionpower, i.e., the first data channel transmission power, based on thesecond data channel transmission power.

However, the determination process may also be performed by the secondwireless device, and only the determination result is transmitted to thefirst wireless device.

That is, in this case, the second wireless device acquires its ownsecond data channel transmission power. Then, the second wireless devicedetermines the first data channel transmission power based on the seconddata channel transmission power, with the power control method accordingto any one of the above embodiments. And then, the second wirelessdevice incorporates the determination result, that is, the first datachannel transmission power, into the power control information, andtransmit the power control information to the first wireless device.Accordingly, the first wireless device receives the power controlinformation indicating the first data channel transmission power, andcontrols the data channel transmission power of the first wirelessdevice according to the first data channel transmission power. Forexample, the first wireless device controls its own data channeltransmission power to be the first data channel transmission power.

With this variant of the present disclosure, the processing load on thefirst wireless device can be reduced.

The above embodiments of the present disclosure are only exemplarydescription, and their specific structures and operations do not limitthe scope of the disclosure. Those skilled in the art can recombinedifferent parts and operations of the above respective embodiments toproduce new implementations which equally accord with the concept of thepresent disclosure.

The embodiments of the present disclosure may be implemented byhardware, software and firmware or in a combination thereof, and the wayof implementation does not limit the scope of the present disclosure.

The connection relationships between the respective functional elements(units) in the embodiments of the disclosure do not limit the scope ofthe present disclosure, in which one or multiple functional element(s)or unit(s) may contain or be connected to any other functional elements.

Although several embodiments of the present disclosure has been shownand described in combination with attached drawings above, those skilledin the art should understand that variations and modifications whichstill fall into the scope of claims and their equivalents of the presentdisclosure can be made to these embodiments without departing from theprinciple and spirit of the disclosure.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A power control method, in a clusterincluding a first wireless device, a second wireless device and a thirdwireless device, the method comprising: receiving, at the first wirelessdevice, power control information including a reference signaltransmission power of the second wireless device, from the secondwireless device, wherein the second wireless device is communicable withother wireless devices including the first and third wireless devices;calculating, at the first wireless device, a transmission path lossbetween the first wireless device and the second wireless device usingthe reference signal transmission power of the second wireless deviceand a reference signal received power (RSRP); and determining, at thefirst wireless device, a first data channel transmission power of thefirst wireless device at which to perform communication directly betweenthe first wireless device and the third wireless device, based at leaston the transmission path loss between the first wireless device and thesecond wireless device.
 2. The power control method according to claim1, wherein power control of a control channel is independently performedfrom that of the first data channel.
 3. The power control methodaccording to claim 1, wherein the reference signal transmission power ofthe second wireless device is determined from a minimum value between aRSRP measured at the first wireless device and a RSRP measured at thethird wireless device and from a minimum signal reception power commonto all the wireless devices.
 4. The power control method according toclaim 1, wherein the reference signal transmission power of the secondwireless device is determined from a RSRP measured at the secondwireless device, a reference signal transmission power of the firstwireless device, and a minimum signal reception power common to all thewireless devices.
 5. The power control method according to claim 4,wherein the reference signal transmission power of the second wirelessdevice is determined from a minimum value between the RSRP measured atthe second wireless device and a RSRP measured at the third wirelessdevice, the reference signal transmission power of the first wirelessdevice, and the minimum signal reception power common to all thewireless devices.
 6. The power control method according to claim 1,wherein the first and third wireless devices perform device-to-device(D2D) communication.
 7. A first wireless device comprising: a receiverwhich, in operation, receives power control information including areference signal transmission power of a second wireless device, fromthe second wireless device, wherein the second wireless device iscommunicable with other wireless devices including the first wirelessdevice and a third wireless device; and a controller, coupled to thereceiver, which, in operation, calculates a transmission path lossbetween the first wireless device and the second wireless device usingthe reference signal transmission power of the second wireless deviceand a reference signal received power (RSRP), and determines a firstdata channel transmission power of the first wireless device at which toperform communication directly between the first wireless device and thethird wireless device, based at least on the transmission path lossbetween the first wireless device and the second wireless device.
 8. Thefirst wireless device according to claim 7, wherein the controllerperforms power control of a control channel independently from that ofthe first data channel.
 9. The first wireless device according to claim7, wherein the reference signal transmission power of the secondwireless device is determined from a minimum value between a RSRPmeasured at the first wireless device and a RSRP measured at the thirdwireless device and from a minimum signal reception power common to allthe wireless devices.
 10. The first wireless device according to claim7, wherein the reference signal transmission power of the secondwireless device is determined from a RSRP measured at the secondwireless device, a reference signal transmission power of the firstwireless device, and a minimum signal reception power common to all thewireless devices.
 11. The first wireless device according to claim 10,wherein the reference signal transmission power of the second wirelessdevice is determined from a minimum value between the RSRP measured atthe second wireless device and a RSRP measured at the third wirelessdevice, the reference signal transmission power of the first wirelessdevice, and the minimum signal reception power common to all thewireless devices.
 12. The first wireless device according to claim 7,which, in operation, performs device-to-device (D2D) communication withthe third wireless device.